The present invention relates to a device and a method for determining a corrected offset value.
Adaptive cruise control (ACC) for a vehicle regulates the distance maintained from the vehicle in front as a function of vehicle speed. A method is described in German Published Patent Application No. 197 22 947 from this field, whereby, among other things, the future course of a vehicle including an ACC system is taken into account in the ACC regulation. To do so, the future course range of at least one vehicle driving in front is determined, and then a lateral transverse offset is determined in relation to all vehicles detected. In steady-state road surface curvature conditions, i.e., when traveling along a straight route or in an area of constant curvature in a turn, the future driving corridor is easily determined using the conventional method with the help of a yaw rate signal or a rotational rate signal.
German Published Patent Application No. 196 36 443 describes a system for monitoring sensors in a vehicle. This system includes an arrangement with which identically defined comparison quantities for the sensors are determined for at least two sensors, starting from at least the signals generated by them. Furthermore, the system includes an additional arrangement with which a reference quantity is determined as a function of the comparison quantities at least thus determined. Starting from at least the reference quantity thus determined, monitoring is performed in a monitoring arrangement for at least one sensor. In addition to the monitoring arrangement, the system also includes an arrangement with which the signal generated by it is corrected for at least one sensor, at least as a function of the reference quantity.
German Published Patent Application No. 44 19 364 describes a method of realtime determination of the offset of a test signal. The test signal is determined in the form of digital measured values at fixed time intervals. The measured values are stored in a histogram over a fixed period of time. A measured value range measured most frequently in the fixed period of time is determined as the offset time of the test signal.
The present invention relates to a method of determining the offset value of the output signal of a vehicle sensor,
in which the values of the output signal of the vehicle sensor are determined,
in which the value range of the output signal of the vehicle sensor is divided into at least two partial ranges (intervals, classes),
in which the values of the output signal are allocated to the partial ranges,
in which the number of number quantities representing the values of the output signal allocated to the partial ranges is determined.
The present invention may provide that the number quantities are determined by at least one low-pass filter. Determination by a low-pass filter is described because it is possible to implement low-pass functions without any great complexity, e.g., in controller software.
An example embodiment is characterized in that
a separate low-pass filter is allocated to the at least two partial ranges (intervals, classes),
each of the low-pass filters determines the number quantity allocated to its partial range.
This method may use one or more low-pass filters having an exponential characteristic (this is related to the fact that low-pass filters having an exponential characteristic are especially suitable for use as counters).
An example embodiment is characterized in that
the low-pass filter, in whose allocated partial range the value of the output signal determined at a sampling time falls, is triggered with a first input signal, and
the low-pass filters, in whose allocated value ranges the value of the output signal determined at the same sampling time does not fall, are triggered with a second input signal,
the second input signal differing from the first input signal.
After determining the partial range in which the sensor value thus obtained falls, the various low-pass filters may be triggered easily with different input signals. Due to the different input signals (e.g., 0 or 1), there are different output signals of the low-pass filters. This may also be desirable, because the filling of the individual histogram classes (=partial ranges) changes during the counting operation.
An example embodiment of the present invention is based on the fact that
as a result of triggering of the low-pass filter with a first input signal (k=1), the number quantity determined by this low-pass filter is incremented, and
as a result of triggering of the low-pass filters with a second input signal (k=0), the number quantities determined by these low-pass filters is decremented.
Decrementing the number quantities in the low-pass filters not instantaneously affected by the filling operation ensures that not all low-pass filters will achieve extremely high counts in the course of time.
Another example embodiment of the present invention is based on the fact that
a first average is determined by a first method from at least two successively determined values of the output signal of the vehicle sensor, and
instead of the values of the output signal of the vehicle sensor, the averages obtained by the first method are allocated to the partial ranges.
Thus, instead of using the output signals of the vehicle sensor itself, averages of these output signals are used in the histogram. This makes it possible to filter out any high-frequency interference that might occur, which in turn has a positive effect on the stability of the method.
For example, the vehicle sensor may be a rotational rate sensor which detects the yawing motion of the vehicle. The offset value thus determined may be used for automatic distance regulation and/or control (ACC) in the motor vehicle.
An example embodiment is characterized in that
the offset value is determined by forming a weighted average, and
the partial range (interval, class) having the largest number quantity plus at least one adjacent interval (class) are taken into account in forming the weighted average.
In this manner, the offset value may be determined more reliably and in a more stable manner than if only the partial range having the largest number quantity is taken into account. This is related to the fact that variance effects (i.e., the scatter band of the data) may now also be taken into account.
An example embodiment is characterized in that the linear or quadratic values of the number quantities enter into the weighting factors of the weighted average. This method is very simple to implement.
This method according to the present invention may be used in parallel with other methods of determining the offset value. It is possible to determine a more accurate corrected or averaged offset value by combined or parallel use of different methods of determining the offset value. This may be performed, for example, by forming the average.
The vehicle sensor is a sensor that detects at least one motion of a vehicle. At least two analyses of the output signal performed at at least two different points in time enter into the determination of the offset value
The determination of the offset value is based on a sorting of at least two of these analyses of the output signal.
In the present invention, the motion values representing the motion of the vehicle may be determined by the analysis of the output signal. The sorting operation may be implemented by sorting the motion values thus determined according to size.
At least a subset of possible motion values obtainable by analysis of the output signal (xcfx89) of the vehicle sensor (21b) may be divided into at least two intervals. The determination of the offset value may be based on the allocation of the motion values obtained by the analysis of the output signal to the intervals, and the determination of the offset value may be based on the number of motion values allocated to the intervals.
In analysis of the respective number of motion values allocated to the at least two intervals, the interval having the greatest number of allocated motion values may be determined, and the offset value may be determined as a function of this interval thus determined.
The offset value may be determined by forming a weighted average. The interval having the greatest number of allocated motion values as well as at least one adjacent interval may be taken into account in this formation of the weighted average, for example.
The linear or quadratic values of the number of allocated motion values may enter into the weighting factors of the weighted average.
The number of motion values allocated may be limited to a certain value range by low-pass filtering. In an example embodiment, it may be low-pass filtering having an exponential characteristic.
In addition, at least one subset of possible motion values obtainable by analysis of the output signal of the vehicle sensor is divided into at least two intervals. The determination of the offset value is based on the allocation of the motion values obtained by analysis of the output signal to the intervals and to low-pass filtering.
In this low-pass filtering, a low-pass filter having an exponential characteristic may be used.
An example embodiment of the present invention is illustrated in the following drawing and explained in greater detail in the following description.